Recently, a card type optical recording medium (to be called an "optical memory card" hereinafter), arranged in such a manner that a plurality of tracks are formed in a recording region provided on a card type substrate so that data may be optically read and written along the tracks thus formed, has attracted attention.
A conventional optical memory card has, as shown in FIG.3, a recording region 11, to which data can be written and from which data can be read, on a card type substrate 10 thereof. Furthermore, a multiplicity of elongated tracks 12 are formed in the recording region 11. The recording region 11 is mainly divided into a data region 13 to which data is recorded and a directory region 14 to which recording addresses of the recording data or the like are written.
Each of the tracks 12 in the data recording region 13 is divided into, for example, three blocks 15 as shown in FIG. 4. As a result, when a file (a set of data items) is written to the track 12, the file is divided into sections which correspond to the blocks 15 so that the divided sections are sequentially written. A number recording portion 16 to which the address of each of the blocks 15 is written in the form of a binary code is formed in the leading portion of each of the blocks 15 so that the blocks 15 can be distinguished from one another. In the case of a write error, the same address as that for the erroneous block is written to the next block. As a result, it is arranged in such a manner that, if the same address are successively read, the latter block is read.
As shown in FIG. 5, a file entry 20 to which the name and the attribute of the file are recorded, a start block number portion 21, to which the address of the first block 15 to which the above-described file is written, is written and an end block number portion 22 to which the address of the last block 15 is written, are formed in each of the tracks 12 in the directory region 14 in such a manner that they correspond to the file recorded to the data recording region 13.
The optical memory card structured as described above sometimes includes a defective block in which data cannot be written and read from the track 12 of the data recording region 13. Therefore, when data is desired to be read, the good or bad condition of the block 15 is determined whenever the block 15 is accessed. If it has been determined that the subject block 15 is defective, the reading of that block 15 is neglected and the next block 15 is accessed. Therefore, when the conventional optical memory card is accessed, all of the blocks 15 must be accessed so as to determine the good or bad condition of all of the blocks 15 before data is read. As a result, a problem arises in that the reading speed may be deteriorated by a degree corresponding to the number of accessing of the defective blocks.
Furthermore, another problem arises in that the data capacity becomes reduced since the address must be written to the blocks 15 in the data recording region 13.